A number of methods for decontaminating disposable filtering face piece respirators have been explored for use in health care settings during epidemics where respirators are in short supply, such as the current Covid-19 pandemic. Heating to temperatures above 65 degrees C has been shown to successfully inactivate the SARS-CoV-2 virus on various surfaces. Ovens or similar heating devices are likely already widely available in hospitals globally. We did a quantitative fit test on nine models of

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... P2 and FFP3 respirators before and after heat treatment in an oven. These included both flat fold and moulded cup styles. All passed the initial fit test, and all but two passed the post-treatment fit test. This study demonstrates that FFP respirators can still retain both filtration efficiency and fit after wear and heat treatment, but that it is necessary to understand the probability for failure of fit after decontamination. Heat shows promise as a simple and effective way of treating FFP respirators. Further evaluation of longer-term wear and disinfection effectiveness of heat treatment should be done before widespread use.